Apparatus and methods for deployment of multiple custom-length prostheses

ABSTRACT

Apparatus for delivering stents to body lumens include one or more tubular prostheses carried at the distal end of a catheter shaft, a sheath slidably disposed over the prostheses, and a guidewire tube extending from within the sheath to the exterior of the sheath through an exit port in a sidewall thereof. A guidewire extends slidably through the guidewire tube. The sheath can be moved relative to the catheter shaft and the guidewire tube to expose the prostheses for deployment. Methods of delivering stents are also provided.

RELATED APPLICATION DATA

This application claims the benefit of U.S. Provisional Application Ser.No. 60/688,896, filed on Jun. 8, 2005, and entitled “Apparatus andMethods for Deployment of Multiple Custom-Length Prostheses,” whichapplication is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

This invention relates generally to vascular catheters, and morespecifically to stents and stent delivery catheters for deployment inthe coronary arteries and other vessels.

BACKGROUND OF THE INVENTION

Stenting has become an increasingly important treatment option forpatients with coronary artery disease. Stenting involves the placementof a tubular prosthesis within a diseased coronary artery to expand thearterial lumen and maintain the patency of the artery. Early stenttechnology suffered from problems with restenosis, the tendency of thecoronary artery to become re-occluded following stent placement.However, in recent years, restenosis rates have decreased dramatically.As a result, the number of stenting procedures being performed in theUnited States, Europe, and elsewhere has soared.

Stents are delivered to the coronary arteries using long, flexiblevascular catheters typically inserted through a femoral artery. Forself-expanding stents, the stent is simply released from the deliverycatheter and it resiliently expands into engagement with the vesselwall. For balloon expandable stents, a balloon on the delivery catheteris expanded which expands and deforms the stent to the desired diameter,whereupon the balloon is deflated and removed.

Current stent delivery technology, however, suffers from a number ofdrawbacks. For example, current stent delivery catheters are not capableof customizing the length of the stent in situ to match the size of thelesion to be treated. While lesion size may be measured prior tostenting using angiography or fluoroscopy, such measurements may beinexact. If a stent is introduced that is found to be of inappropriatesize, the delivery catheter and stent must be removed from the patientand replaced with a different device of correct size.

Moreover, current stent delivery devices cannot treat multiple lesionswith a single catheter. Current devices are capable of delivering only asingle stent with a single catheter, and if multiple lesions are to betreated, a new catheter and stent must be introduced for each lesion tobe treated.

Further, current stent delivery devices are not well-adapted fortreating vascular lesions that are very long and/or in curved regions ofa vessel. Current stents have a discrete length that is relatively shortdue to their stiffness. If current stents were made longer so as totreat longer lesions, they would not conform well to the curvature ofvessels or to the movement of vessels on the surface of the beatingheart. On the other hand, any attempt to place multiple stentsend-to-end in longer lesions is hampered by the inability to maintainappropriate inter-stent spacing and to prevent overlap of adjacentstents.

Additionally, some stent delivery catheters and angioplasty ballooncatheters, particularly those having movable external sheaths to enclosethe stent or balloon, suffer from poor tracking and cumbersomeinteraction with guidewires. Some such catheters utilize an“over-the-wire” design in which the guidewire extends through an innerlumen of the catheter from its proximal end to its distal end, a designthat makes catheter exchanges cumbersome and time-consuming. Rapidexchange designs have also been proposed for such catheters wherein theguidewire extends through the distal end of the catheter and out througha port in a sidewall of the sheath. However, in these designs theguidewire inhibits smooth retraction of the sheath and, if the sheath isretracted a substantial distance, the port can become so displaced fromthe distal end of the catheter that the guidewire does not slidesmoothly as the catheter is moved.

Finally, many stent delivery catheters suffer from inflexibility andhigh cross-sectional profile, which hamper endovascular positioning.

For these and other reasons, stents and stent delivery catheters areneeded which enable the customization of stent length in situ, and thetreatment of multiple lesions of various sizes, without requiringremoval of the delivery catheter from the patient. Such stents and stentdelivery catheters should be capable of treating lesions of particularlylong length and lesions in curved regions of a vessel, and should behighly flexible to conform to vessel shape and movement. Such stentdelivery catheters should further be of minimal cross-sectional profileand should be highly flexible for endovascular positioning throughtortuous vascular pathways.

BRIEF SUMMARY OF THE INVENTION

The invention provides apparatus and methods for delivering prosthesesor stents into body lumens. In one aspect of the invention, an apparatusfor delivering a prosthesis into a target vessel comprises a flexiblecatheter shaft having proximal and distal ends and a first lumentherein. A tubular prosthesis is releasably carried near the distal endof the catheter shaft and is expandable to a shape suitable for engagingthe target vessel. A sheath is disposed over the catheter shaft and thetubular prosthesis and is axially movable relative thereto. The sheathhas proximal and distal ends, a sidewall, and an exit port in thesidewall between the proximal and distal ends. A guidewire tube extendsthrough the exit port and has a distal extremity disposed within thetubular prosthesis and a proximal extremity disposed outside of thesheath, the guidewire tube being adapted for slidably receiving aguidewire therethrough.

Preferably, the guidewire tube is slidable through the exit port so thatthe sheath slides relative to the guidewire tube as it is retracted toexpose the prosthesis for deployment. Usually the guidewire tube isfixed relative to the catheter shaft, and may be attached thereto. If anexpandable member is mounted to the catheter shaft for prosthesisexpansion, the guidewire tube may extend through and attach to theexpandable member.

Because the guidewire tube exits the sheath in a distal extremitythereof the sheath has a low profile portion proximal to the exit portthat has a smaller diameter than the portion distal to the exit port.Not only does this reduce the cross-sectional profile, but increases theflexibility of the device.

The exit port may be cut into the sidewall of the sheath to facelaterally, or alternatively oriented so as to face generally in aproximal direction. The exit port is usually positioned so as to becloser to the distal end of the sheath than to the proximal end thereof,and is preferably a distance of about 20-35 cm from the distal end ofthe sheath. With the sheath advanced fully distally over the cathetershaft, the proximal extremity of the guidewire tube exposed outside thesheath is preferably about 3-15 cm in length, although various lengthsare possible, even as long or longer than the catheter shaft itself. Theproximal end of the guidewire tube is preferably disposed a distance ofless than about one-half the length of the catheter shaft from thedistal end thereof, but in some embodiments may extend furtherproximally, even as far as the proximal end of the catheter shaft.

The apparatus of the invention may be configured to deliver tubularprostheses that are either self-expanding or expandable by a balloon orother expandable member. When self-expanding prostheses are used, thesheath is adapted to constrain the prosthesis in a collapsedconfiguration. Upon retraction of the sheath, the prosthesis is releasedand self-expands to engage the vessel.

For balloon-expandable prostheses, an expandable member is mounted tothe catheter shaft near the distal end thereof. The tubular prosthesisis positionable over the expandable member for expansion therewith.Usually the expandable member will comprise a balloon in communicationwith an inflation lumen in the catheter shaft for delivery of inflationfluid to the balloon. The sheath is axially positionable relative to theexpandable member and configured to restrain expansion of a selectedportion of the expandable member. Preferably the sheath is reinforced toprevent expansion thereof by the expandable member.

In a preferred aspect of the invention, the tubular prosthesis comprisesa plurality of prosthesis segments. The sheath is axially movablerelative to the prosthesis segments and configured to restrain expansionof a selectable number of prosthesis segments. In this way, lesions ofvarious lengths may be treated by adjusting the length of the prosthesisin situ, without removal of the device from the body. In theseembodiments, a pusher may be slidably disposed within the sheathproximal to the tubular prosthesis. The pusher has a distal end inengagement with the tubular prosthesis for moving the tubular prosthesisrelative to the catheter shaft.

In a further aspect of the invention, a method of delivering aprosthesis in a target vessel of a patient comprises inserting aguidewire through the patient's vasculature to the target vessel;slidably coupling a delivery catheter to the guidewire, the deliverycatheter having a sheath and a guidewire tube, a proximal extremity ofthe guidewire tube being outside the sheath and a distal extremity ofthe guidewire tube being inside the sheath, the guidewire being slidablypositioned through the guidewire tube; advancing the delivery catheterover the guidewire to the target vessel; retracting the sheath relativeto the guidewire tube to expose a tubular prosthesis carried by thedelivery catheter; and expanding the tubular prosthesis into engagementwith the target vessel.

Usually, the guidewire tube will extend through an exit port in thesheath, and the guidewire tube will slide through the exit port as thesheath is retracted. The method may include sealing the exit port aroundthe guidewire tube to restrict fluid flow therethrough, but preferablythe exit port allows some fluid flow to provide flushing of the distalportion of the catheter.

In a preferred embodiment, an expandable member is fixed to a distalportion of the guidewire tube and the tubular prosthesis is positionableover the expandable member. The sheath is slidably disposed over theprosthesis and the expandable member and may be retracted a selectabledistance to expose a desired length of the prosthesis and expandablemember. The tubular prosthesis will then be expanded by expanding theexpandable member. The sheath may be used to cover a proximal portion ofthe expandable member to constrain the proximal portion from expansionwhile a distal portion of the expandable member expands. Usually, theexpandable member is inflatable and will be inflated by deliveringinflation fluid to the expandable member through an inflation lumen inthe catheter shaft. The guidewire tube preferably extends through theinterior of the expandable member, which may be attached to theguidewire tube.

In a preferred aspect of the invention, the tubular prosthesis comprisesa plurality of prosthesis segments, and the method includes positioninga first selected number of the prosthesis segments on the expandablemember for expansion therewith. The method may further includepositioning the sheath over a second selected number of the prosthesissegments to constrain expansion thereof. The first selected number ofprosthesis segments may be positioned on the expandable member bypushing the first selected number with a pusher that is axially slidablerelative to the expandable member.

In alternative embodiments, the tubular prosthesis self-expands when thesheath is retracted. In embodiments in which the prosthesis comprisesmultiple prosthesis segments, the sheath may be retracted relative to aselected number of such segments to allow the segments to self-expandinto contact with the vessel.

In another aspect, the invention provides a balloon catheter fortreating a target vessel that includes a flexible catheter shaft havingproximal and distal ends and a first lumen therein. An expandable memberis connected to the catheter shaft, and a sheath is disposed over thecatheter shaft and the expandable member and is axially movable relativethereto. The sheath has an exit port in a sidewall thereof between itsproximal and distal ends. A guidewire tube extends through the exit portand has a proximal extremity disposed outside of the sheath and a distalextremity disposed within the sheath that is coupled to the cathetershaft or the expandable member or both. The guidewire tube is adaptedfor slidably receiving a guidewire therethrough. The expandable memberpreferably comprises a balloon in fluid communication with the firstlumen to receive inflation fluid therefrom. The sheath may bepositionable to constrain a first selected portion of the expandablemember from expansion while a second selected portion of the expandablemember expands.

In a preferred embodiment of the balloon catheter of the invention, atubular prosthesis is disposed on the expandable member and isexpandable therewith. The tubular prosthesis will preferably comprise aplurality of unconnected stent segments that are slidable relative tothe expandable member. The sheath is positionable to expose a firstselected portion of the stent segments while covering a second selectedportion of the stent segments.

In yet another aspect of the invention, an apparatus for delivering aprosthesis into a target vessel comprises a flexible catheter shafthaving proximal and distal ends and a tubular prosthesis slidablycoupled to the catheter shaft, the tubular prosthesis being expandableto a shape suitable for engaging the target vessel. A pusher is providedfor moving the tubular prosthesis from a pre-deployment position to adeployment position near the distal end of the catheter shaft. Theapparatus further includes a stop on the catheter shaft configured toengage the tubular prosthesis when the tubular prosthesis is in thedeployment position.

In one embodiment, an expandable member is coupled to the catheter shaftand the tubular prosthesis is adapted for expansion by the expandablemember. The expandable member, e.g. balloon, has an interior, and thestop is preferably disposed within the interior of the expandablemember. The stop may also be disposed outside of or on the exteriorsurface of the expandable member. Alternatively, the tubular prosthesisis self-expanding and expands upon being released from the cathetershaft.

In a preferred aspect, a plurality of tubular prostheses are slidablycoupled to the catheter shaft and are movable by the pusher to thedeployment position. In addition, a sheath may be movably coupled to thecatheter shaft and positionable over the tubular prosthesis orprostheses.

In a further method of deploying a tubular prosthesis in a target vesselaccording to the invention a catheter shaft is positioned in a targetvessel and the tubular prosthesis is moved distally relative to thecatheter shaft while the catheter shaft remains in the target vesseluntil the prosthesis engages a stop near the distal end of the cathetershaft. The tubular prosthesis is then expanded to engage a wall of thetarget vessel.

After expanding the tubular prosthesis, a second prosthesis (or anynumber of additional prostheses) may be moved distally relative to thecatheter shaft until the second prosthesis engages the stop, and thesecond prosthesis then expanded to engage a wall of the target vessel.Alternatively, a second prosthesis may be moved distally relative to thecatheter shaft simultaneously with moving the tubular prosthesis, andboth the second prosthesis and the tubular prosthesis are expandedtogether to engage the wall of the target vessel. Usually, the tubularprosthesis and any additional prostheses are moved by a pusher movablycoupled to the catheter shaft.

The tubular prosthesis is preferably expanded by inflating a ballooncoupled to the catheter shaft. Alternatively, the tubular prosthesis maybe self-expandable.

Further, the method may include retaining a second prosthesis in anunexpanded configuration on the catheter shaft while the tubularprosthesis is expanded. In one embodiment, the second prosthesis isretained within a sheath movably coupled to the catheter shaft.

Further aspects of the nature and advantages of the invention willbecome apparent from the detailed description below taken in conjunctionwith the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a stent delivery catheter according tothe invention with sheath retracted and expandable member inflated.

FIG. 2A is a side cross-section of a distal portion of the stentdelivery catheter of FIG. 1 with expandable member deflated and sheathadvanced distally.

FIG. 2B is a side cross-section of a distal portion of the stentdelivery catheter of FIG. 1 with expandable member inflated and sheathretracted.

FIG. 2C is a side cross-section of a distal portion of a stent deliverycatheter illustrating radiopaque markers attached to the guidewire tube.

FIG. 3 is a transverse cross-section through line 3-3 of FIG. 2A.

FIG. 4 is a transverse cross-section through line 4-4 of FIG. 2A.

FIG. 5A is a side view of a first embodiment of a stent segmentaccording to the invention in an unexpanded configuration.

FIG. 5B is a side view of the stent segment of FIG. 5A in an expandedconfiguration.

FIG. 6A is a side view of a second embodiment of a stent segmentaccording to the invention in an unexpanded configuration.

FIG. 6B is a side view of two of the stent segments of FIG. 6A in anexpanded configuration.

FIGS. 7A-7E are side cut-away views of the stent delivery catheter ofthe invention positioned in a vessel with the stent segments of FIGS.5A-5B, illustrating various steps of delivering a prosthesis accordingto the method of the invention.

FIG. 8 is a side cut-away view of the stent delivery catheter of theinvention positioned in a vessel with the stent segments of FIGS. 6A-6Bin a deployed configuration.

FIG. 9 is a perspective view of the distal portion of the stent deliverycatheter of the invention with a portion of the outer sheath strippedaway to reveal a garage member.

FIG. 9A is an end view of a stop member.

FIG. 10 is a planar view of a garage member.

FIG. 11 is a side view of a garage member attached to a pair ofmandrels.

FIG. 12A is a side view of an expandable member in its expanded state.

FIG. 12B is a side view of an expandable member in its contracted stateand having a plurality of stent segments thereon.

FIG. 12C is a side cross-section of an expandable member according tothe invention.

FIG. 13 is a side view of a pusher tube.

FIG. 13A is a cross-sectional view of the pusher tube of FIG. 13 takenat line A—A.

FIGS. 14A-B are side views of a stent segment embodiment havingradiopaque markers affixed thereto.

FIGS. 15A-C are side views of stent segment embodiments havingradiopaque marker coatings applied thereto.

FIGS. 15D-E are side views of multiple stent segments in their expandedconfigurations having radiopaque marker coatings applied thereto.

FIG. 16 is a side view of a slider tube.

FIG. 16A is a cross-sectional view of the slider tube of FIG. 16 takenat line A-A.

FIG. 17 is a side view of a slider body.

FIG. 17A is a cross-sectional view of the slider body of FIG. 17 takenat line A-A.

FIG. 17B is an end view of the slider body of FIG. 17.

FIG. 18 is a side view of a slider cap.

FIG. 18A is an end view of the slider cap of FIG. 18.

FIG. 19 is a perspective view of a slider seal.

DETAILED DESCRIPTION OF THE INVENTION

The present application relates generally to copending U.S. patentapplication Ser. No. 10/637,713, entitled “Apparatus and Methods forDeployment of Vascular Prostheses,” filed Aug. 8, 2003, whichapplication is hereby incorporated by reference.

A first embodiment of a stent delivery catheter according to presentinvention rated in FIG. 1. Stent delivery catheter 20 includes acatheter body 22 comprising sheath 25 slidably disposed over an innershaft 27 (not shown in FIG. 1). An expandable member 24, preferably aninflatable balloon (shown in an inflated configuration), is mounted toinner shaft 27 and is exposed by retracting sheath 25 relative to innershaft 27. A tapered nosecone 28, composed of a soft elastomeric materialto reduce trauma to the vessel during advancement of the device, ismounted distally of expandable member 24. A stent 30, which preferablycomprises a plurality of separate or separable stent segments 32, isdisposed on expandable member 24 for expansion therewith. A guidewiretube 34 is slidably positioned through a guidewire tube exit port 35 insheath 25 proximal to expandable member 24. A guidewire 36 is positionedslidably through guidewire tube 34, expandable member 24, and nosecone28 and extends distally thereof.

A handle 38 is attached to a proximal end 23 of the sheath 25. Thehandle 38 performs several functions, including operating andcontrolling the catheter body 22 and the components included in thecatheter body. Various embodiments of a preferred handle and additionaldetails concerning its structure and operation are described inco-pending pending U.S. patent application Ser. No. 11/148,713, filedJun. 8, 2005, (Attorney Docket No. 14592.4002), entitled “Devices andMethods for Operating and Controlling Interventional Apparatus,” whichapplication is hereby incorporated herein by reference. Embodiments ofanother preferred handle and details concerning its structure andoperation are described in co-pending U.S. application Ser. No.10/746,466, filed Dec. 23, 2003 (Attorney Docket No. 021629-002200US),entitled “Devices and Methods for Controlling and Indicating the Lengthof an Interventional Element,” which application is also herebyincorporated herein by reference.

The handle 38 includes a housing 39 that encloses the internalcomponents of the handle. The inner shaft 27 is preferably fixed to thehandle, while the outer sheath 25 is able to be retracted and advancedrelative to the handle 38. An adaptor 42 is attached to the handle 38 atits proximal end, and is fluidly coupled to the inner shaft 27 in theinterior of the housing of the handle 38. The adaptor 42 is configuredto be fluidly coupled to an inflation device, which may be anycommercially available balloon inflation device such as those sold underthe trade name “Indeflator™”, available from Guidant Corp. of SantaClara, Calif. The adaptor is in fluid communication with the expandablemember 24 via an inflation lumen in the inner shaft 27 to enableinflation of the expandable member 24.

The outer sheath 25 and guidewire 36 each extend through a sliderassembly 50 located on the catheter body 22 at a point between itsproximal and distal ends. The slider assembly 50 is adapted forinsertion into and sealing within a hemostatic valve, such as on anintroducer sheath or guiding catheter, while allowing relative movementof the outer sheath 25 relative to slider assembly 50. The sliderassembly 50 includes a slider tube 51, a slider body 52, and a slidercap 53. These components are illustrated in greater detail in FIGS.16-19.

In particular, FIGS. 16 and 16A show the slider tube 51, which comprisesan elongated cylindrical member having a first through-hole 51 a and asecond through-hole 51 b. The first through-hole 51 a has a size toprovide a slidable passageway for the catheter body 22, whereas thesecond through-hole 51 b has a size to provide a slidable passageway forthe guidewire 34. The slider tube 51 is preferably formed from apolymeric material, such as PTFE, FEP, polyimide, nylon, or Pebax. Theslider body 52 is illustrated in FIGS. 17 and 17A-B. The slider body 52is also an elongated member having a cylindrical section 160 and atapered section 161. The tapered section 161 has an internal recess 161a that has an interior diameter that provides a snug fit with theexternal surface of the slider tube 51. The cylindrical section 160 hasan internal recess 160 a that has an interior diameter that provides asnug fit with the external surface of the slider cap 53. The slider body52 also includes a first through-hole 52 a sized to allow slidablepassage of the catheter body 22, and a second through-hole 52 b sized toallow passage of the guidewire 34. The slider body is preferably formedfrom a resilient, relatively incompressible material, such aspolycarbonate, and has an exterior surface adapted for being clamped andsealed within a hemostasis valve, preferably being smooth andcylindrical in shape. The slider cap 53 is a relatively shortcylindrical member having a first through-hole 53 a sized to allowslidable passage of the catheter body 22, and a second through-holesized to allow slidable passage of the guidewire 34. The slider cap 53has a size that provides a snug fit with the internal recess 160 a ofthe cylindrical section 160 of the slider body. The slider cap 53 isalso preferably formed of a resilient, relatively incompressiblematerial, such as polycarbonate.

A slider seal 54 is illustrated in FIG. 19. The slider seal is a short,disc-shaped member having a size adapted to fit snugly within theinternal recess 160 a of the cylindrical section 160 of the slider body.The slider seal 54 includes a first through-hole 54 a sized to allowfluidly sealed, slidable passage of the catheter body 22, and a secondthrough-hole 54 b sized to allow fluidly sealed, slidable passage of theguidewire 34. The slider seal is preferably formed of a pliable,resilient material, such as a polymeric material or a silicone compoundthat is capable of providing a fluid-tight seal with the sheath andguidewire while allowing slidable movement thereof.

The slider assembly 50 is constructed by installing the proximal end ofthe slider tube 51 into the internal recess 161 a of the tapered portion161 of the slider body, taking care to align the first and secondthrough-holes of each member appropriately. The slider seal 54 isinstalled in the internal recess 160 a of the cylindrical portion 160 ofthe slider body, and the slider cap 53 is placed over the slider seal 54within the internal recess 160 a, again taking care to ensure that thefirst and second through-holes of each component are properly aligned.The components are then bonded together by heating or by use ofadhesives or other suitable means. The completed slider assembly 50 isthen placed over the catheter body 22 and the guidewire 34 as shown inFIG. 1.

Referring now to FIGS. 2A-2B, 3 and 4, which show a distal portion ofthe stent delivery catheter in cross-section, it may be seen that sheath25 may be extended up to nosecone 28 to fully surround expandable member24 and stent segments 32. A garage 55 is attached to the outer sheath 25at the distal end 57 of the sheath. The garage 55 is a generallycylindrical member having a relatively high circumferential strengthsuch that it is able to prevent the expandable member 24 from inflatingwhen the garage is extended over the inflatable member 24. The garage 55preferably has a length at least as long as one of the stent segments 32carried by the catheter, but preferably less than the combined length oftwo such stent segments. The garage 55 is shown in more detail in FIGS.9-11, and is described more fully below. A radiopaque marker 56 ispreferably formed integrally with or attached to the distal end of thegarage 55 to facilitate visualization of the position of the sheath 25using fluoroscopy. The radiopaque marker 56 may have an axial lengthselected to provide a visual reference for determining the appropriatedistance for stent segment separation, e.g., 2-4 mm, as described below.

The outer sheath 25 further includes a valve member 58 within the garage55 preferably spaced proximally from the distal end 57 a distance equalto, slightly larger than, or slightly smaller than the length of one ofthe stent segments 32. For example, in a preferred embodiment, eachstent segment 32 has a length of about 4 mm, and the valve member 58 islocated approximately 5 mm from the distal end 57 of the sheath or thedistal end of the garage member 55. In other embodiments, the valvemember 58 may be spaced from the distal end 57 a distance equal to about¼-¾ of the length of one stent segment 32, more preferably one-half thelength of one stent segment 32. Valve member 58 preferably comprises anecked-down circumferential waist or inwardly extending ring-shapedflange 60 configured to frictionally engage stent segments 32 andthereby restrict the sliding movement of stent segments 32 distallyrelative to sheath 25. Flange 60 may be a polymeric or metallic materialintegrally formed with sheath 25 or, preferably, with the garage 55, ora separate annular member bonded or otherwise mounted to the interior ofthe sheath 25 or the garage 55. The geometry of flange 60 may betoroidal with circular cross-section (like an O-ring) or it may haveanother cross-sectional shape such as triangular, trapezoidal, orpyramidal. Preferably flange 60 is a polymer such as silicone orurethane sufficiently soft, compliant, and resilient to providefrictional engagement with stent segments 32 without damaging the stentsegment or any coating deposited thereon. Valve member 58 will extendradially inwardly a sufficient distance to engage the exterior of stentsegments 32 with sufficient force to allow the line of stent segments 32remaining within sheath 25 to be retracted proximally with sheath 25 soas to create spacing relative to those stent segments disposed distallyof sheath 25 for deployment. At the same time, valve member 58 shouldnot exert so much force that it removes or damages the coating on theexterior surface of stent segments 32 as sheath 25 is retracted relativeto the stent segments to expose a desired number of stent segments 32.In a preferred embodiment, stent segments 32 have an outer diameter ofabout 0.040-0.050 in. (including coating) and sheath 25 and garage 55have inner diameter 0.041-0.051 in. so as to provide clearance of about0.001 in. with stent segments 32. Valve member 58 has a preferred innerdiameter about 0.003-0.008 in. less than that of garage 55, or about0.033-0.048″, so as to provide an interference fit with stent segments32. Valve member 58 will preferably exert a force of about 0.5-5 lbs. ona stent segment 32 positioned within it. Various embodiments of valvemember 58 are described in copending application Ser. No. 10/412,714,Filed Apr. 10, 2003 (Attorney Docket No. 21629-000330), which isincorporated herein by reference.

FIGS. 9-11 illustrate the garage 55, the radiopaque marker 56, and thevalve member 58 in greater detail. The garage 55 is a cylindrical memberthat is preferably mounted to the distal end of the outer sheath 25.FIG. 9 illustrates the garage 55 as it is oriented surrounding the stentsegments 32 aligned over the inner shaft. The distal portion of theouter sheath 25 is shown stripped away in FIG. 9 to reveal theorientation of the garage 55. The cylindrical garage 55 is preferablyformed of a metallic, polymeric, or other material and in a geometry toprovide high radial strength and high axial flexibility. Superelasticalloys are preferred materials. A preferred garage material is Nitinol.

The structure of the garage 55 is illustrated in FIG. 10, in which thegarage 55 is shown in a planar form for clarity. The garage 55 ispreferably laser cut from a tube, but may also be cut, stamped, orotherwise formed from a sheet of material.

A number of cut-outs or windows 59 are preferably formed in the body ofthe garage to increase its axial flexibility. Preferably, the garage 55is constructed in a manner and of materials that allow it to bend abouta transverse axis. Although the number, size, and shape of the cut-outs59 may vary, the illustrated embodiment includes a preferred form. Thedistal end 55 a of the garage 55 is provided with no cut-outs in orderto provide the greatest radial strength at the distal end of the sheath,where the restraining force against the expandable member 24 is thegreatest. A pair of first cut-outs 59 a having oval or rectangular shapeare formed a short distance from the distal end 55 a of the garage, thepair of first cut-outs 59 a being aligned circumferentially around theperiphery of the garage. A series of narrow second cut-outs 59 b havinga linear or slot-like shape are formed over the central portion of thebody of the garage 55. Preferably, the second cut-outs 59 b are providedin a staggered formation to provide greater axial flexibility over thecentral portion of the garage. A series of third cut-outs 59 c arelocated just proximally of the central portion of the garage. The thirdcut-outs 59 c are of a similar size and shape to the first cut-outs 59a, but are circumferentially staggered from the first cut-outs 59 a. Aseries of fourth rectangular or oval-shaped cut-outs 59 d are locatedjust proximally of the third cut-outs, and are both narrower and shorterthan the third cut-outs 59 c. Finally, a series of fifth cut-outs 59 ehaving a hexagonal shape are provided near the proximal end 55 b of thegarage. Each of the fifth cut-outs 59 e is substantially wider (i.e.,greater longitudinal length) than the other cut-outs 59 a-d. As notedbelow, the position of the fifth cut-outs corresponds with the locationof the valve member 58.

Turning to FIG. 1, the garage 55 is shown supported on a proximalmandrel 150 and a distal mandrel 152 to facilitate attachment of thevalve member 58 and sheath 25 thereto. The proximal mandrel is providedwith an indentation or concavity adapted to receive and retain the valvemember 58 in place for the purpose of attaching the valve member 58 tothe garage 55 and outer sheath 25. The radiopaque marker 56 may beplaced over the distal end 55 a of the garage 55. After the foregoingcomponents have been properly aligned, the outer sheath 25 is attachedto the proximal end 55 b of garage 55, preferably by placing a piece ofshrink tubing over the garage and distal end of the outer sheath andheating the assembly. The garage 55 is thereby covered with a polymermaterial about its exterior. Of course various other attachmenttechniques may be used including heat treatment, adhesives, or othermethods known to those skilled in the art.

As thus described, the sheath 25 has a distal extremity 62 configured tosurround expandable member 24 and stent segments 32 disposed thereonwhen in an unexpanded configuration. Distal extremity 62 extendsproximally to a junction 63, preferably aligned with the location ofguidewire tube exit port 35, where distal extremity 62 is joined to aproximal extremity 64 that extends proximally to handle 38 (see FIG. 1).In a preferred embodiment, distal extremity 62 has a length of about15-35 cm and proximal extremity 64 as a length of about 100-125 cm.Proximal extremity 64 may be constructed of a variety of biocompatiblepolymers, metals, or polymer/metal composites, preferably beingstainless steel or Nitinol. Distal extremity 62 may be a polymer such asPTFE, FEP, polyimide, nylon, or Pebax, or combinations of any of thesematerials. In a preferred form, the distal extremity 62 comprises acomposite of nylon, PTFE, and polyimide. The distal extremity ispreferably reinforced with a metallic or polymeric braid to resistradial expansion when expandable member 24 is expanded. Sheath 25 mayfurther have a liner surrounding its interior of low friction materialsuch as PTFE to facilitate relative motion of sheath 25, stent segments32, and pusher tube 86.

Preferably, proximal extremity 64 has a smaller transverse dimensionthan distal extremity 62 to accommodate the added width of guidewiretube 34 within the vessel lumen, as well as to maximize flexibility andminimize profile. In one embodiment, shown in FIG. 3, distal extremity62 is a tubular member having a first outer diameter, preferably about1.0-1.5 mm, and proximal extremity 64 is a tubular member having asecond, smaller outer diameter, preferably about 0.7-1.0 mm. At thejunction of proximal extremity 64 with distal extremity 62, aproximally-facing crescent-shaped opening 65 is formed between the twotubular members that creates guidewire tube exit port 35. Excess spacewithin crescent-shaped opening 65 may be filled with a filler materialsuch as adhesive or a polymeric material (e.g., Pebax).

In an alternative embodiment (not shown), a hole is formed in thesidewall of distal extremity 62 or proximal extremity 64 to createguidewire tube exit port 35. Proximally of guidewire tube exit port 35,the wall of sheath 25 adjacent to guidewire tube 34 is flattened orcollapsible inwardly thereby reducing the transverse dimension of sheath25 to accommodate the width of guidewire tube 34.

Guidewire tube 34 is slidably positioned through guidewire tube exitport 35. The guidewire tube exit port 35 may be configured to provide atotal or partial fluid seal around the periphery of guidewire tube 34 tolimit blood flow into the interior of sheath 25 and to limit leakage ofsaline (or other flushing fluid) out of sheath 25. This may beaccomplished by sizing guidewire tube exit port 35 appropriately so asto form a fairly tight frictional seal around guidewire tube 34 whilestill allowing the sliding motion thereof relative to sheath 25.Alternatively an annular sealing ring may be mounted in guidewire tubeexit port 35 to provide the desired seal. Preferably, however, theguidewire tube exit port 35 is not totally fluid sealed, so as toprovide a slight leakage or fluid flow to provide the ability to flushthe distal extremity 62 of the catheter.

Guidewire tube exit port 35 will be positioned to provide optimaltracking of stent delivery catheter 20 through the vasculature andmaximizing the ease with which the catheter can be inserted onto andremoved from a guidewire to facilitate catheter exchanges. Usually,guidewire tube exit port 35 will be positioned at a location proximal toexpandable member 24 when sheath 25 is extended fully distally up tonosecone 28, but a distance of no more than one-half the length ofsheath 25 from distal end 57. In preferred embodiments for coronaryapplications, guidewire tube exit port 35 is spaced proximally adistance of about 20-35 cm from the distal end 57 of sheath 25.

Guidewire tube 34 should extend proximally from guidewire tube exit port35 a distance at least as long as the longest possible stent that may bedeployed, e.g., 30-200 mm depending upon the application, to allow forretraction of sheath 25 that distance while retaining a portion ofguidewire tube 34 external to sheath 25. Preferably the guidewire tube34 extends proximally a distance of about 35 to about 70 mm from theguidewire tube exit port 35 when sheath 25 is in a fully distalposition, with the proximal end thereof disposed a distance of about23-50 cm from the distal tip of nosecone 28. Where stent deliverycatheter 20 is to be positioned through a guiding catheter, the proximalend of guidewire tube 34 will preferably be positioned so as to bewithin the guiding catheter when expandable member 24 is positioned atthe target site for stent deployment. Guidewire tube 34 is preferably ahighly flexible polymer such as PTFE, FEP, polyimide, or Pebax, and mayoptionally have a metal or polymer braid or fiber embedded in it toincrease kink-resistance and tensile strength.

Inner shaft 27 forms an inflation lumen 66 that is in communication withinterior of expandable member 24. The inner shaft 27 may be formed of apolymer material such as PTFE, FEP, polyimide, or Pebax, or the innershaft 27 may be a metal such as stainless steel or Nitinol.

Expandable member 24 has an expandable balloon member 70 that is joinedto a non-expandable tubular leg 72. Expandable balloon member 70 is asemi-compliant polymer such as Pebax, polyurethane, or Nylon.Non-compliant, fully elastic, or other materials such as PTFE may alsobe used. Preferably, the compliance of the balloon member allows theexpanded diameter of balloon member 70 to be adjusted by selecting theappropriate inflation pressure delivered thereto, thereby allowingcustomization of the deployed diameter of stent segments 32. Forexample, in one embodiment, balloon member 70 may be inflated to apressure of between about 5 and about 12 atmospheres, allowing thedeployed stent diameter to be adjusted from about 2.0 mm to 4.0 mm. Ofcourse, larger and smaller stent diameters are also possible byutilizing appropriate stent geometry and applying suitable inflationpressures. Tubular leg 72 is preferably a polymer such as polyimide,PTFE, FEP, polyurethane, or Pebax and may optionally be reinforced witha metal or polymer braid or metal or polymer fibers. Tubular leg 72 hasan open proximal end 74 through which guidewire tube 34 extends.Proximal end 74 of tubular leg 72 is fixed to distal end 68 of innershaft 27 and to guidewire tube 34, forming a fluid-tight seal. Guidewiretube 34 passes through the interior of balloon member 70 and is mountedto nosecone 28, thereby providing a passage through the distal portionof catheter body 22 through which guidewire 36 may pass. Balloon member70 has a distal end 76 that extends over an annular stop 78, which ismounted to the distal end of guidewire tube 34 and/or nosecone 28.Distal end 76 of balloon member 70 may be bonded to stop 78, guidewiretube 34, and/or nosecone 28. The stop 78 has a size and shape selectedto engage stent segment 32 and provide a stop against which stentsegments 32 can be located in the ideal deployment position withoutbeing pushed beyond the distal end of balloon member 70. Additionaldetails concerning stent stops suitable for use in the devices andmethods described herein are disclosed in U.S. patent application Ser.No. 10/884,616, filed Jul. 2, 2004, (Atty. docket 21629-000360), whichis hereby incorporated by reference herein.

Preferably, the stop 78 has a partial cylindrical shape, rather than afull cylindrical shape, as a relief to reduce interference with garage55. For example, FIGS. 9 and 9A illustrate the stop 78 having a flatportion 81 formed on the opposed lateral surfaces of the stop 78. Asimilar flat portion may be formed on the upper and lower sides of thestop 78. The provision of flat portions on the stop 78 allows the stop78 to limit distal movement of the stent segments 32, while reducinginterference between stop 78 and the interior of garage 55.

Optionally, within the interior of balloon member 70 an annular basemember 80 is mounted to guidewire tube 34 and has a diameter selected tourge balloon member 70 against stent segments 32 in their unexpandedconfiguration, thereby providing frictional engagement with stentsegments 32. This helps to limit unintended sliding movement of stentsegments 32 on balloon member 70. Base member 80 may be made of a softelastomer, foam, or other compressible material.

An additional option or alternative structure for limiting unintendedsliding or movement of the stent segments is the provision on the distalexterior portion of the expandable member 24 of a layer of material 84having a high coefficient of friction so as to frictionally engage thestent segments 32. See FIGS. 12A-C. For example, a layer of a polymericmaterial 84, such as polyurethane, will prevent the stent segments 32from sliding off the distal end of the balloon, and will cause the stentsegments 32 to stop in the desired location near the distal end of theexpandable member 24. The layer of material 84 is preferably formed overthe entire circumference of the distal end of the expandable member 24,as shown in the Figures, but may alternatively be placed only at spacedintervals around the periphery. The material layer 84 is preferablyformed of elastomeric materials and in a manner that allows it to expandand contract as the expandable member 24 expands and contracts. Forexample, the material layer 84 may be applied by dipping the expandablemember 24 in a liquid polymer, by spraying, or by attaching a sheet ortube of material over the expandable member 24 by adhesive or heattreatment. As the stent segments 32 move distally relative to theexpandable member 24 in its contracted state, the distal end of the mostdistal stent segment will come into contact with the layer of material84 and the friction force encountered by the stent segment 32 willincrease. This will inhibit or prevent additional relative movementbetween the stent segment 32 and the expandable member 24. In addition,the increased frictional resistance may serve as a tactile indicator tothe user of the position of the stent segment 32 relative to theexpandable member 24. Material layer 84 may be of equal thickness alongit length, or the thickness of the material layer 84 may graduallyincrease in the distal direction to provide gradually increasinginterference with stent segments 32. Material layer 84 may have an outersurface at the same height as the outer surface of expandable member 24to provide a smooth transition therebetween, or material layer 84 may beof greater height to provide a step that enhances engagement with stentsegments 32.

In a preferred embodiment as shown in FIG. 12C, expandable member 24 ismolded with a circumferential channel, stepped geometry, and/or withreduced wall thickness near its distal end so as to have a smaller outerdiameter in the region where the material layer 84 is to be applied toaccommodate the thickness of material layer 84. In this way, the outerwall of the expandable member 24 and material layer 84 will be smoothand continuous without an abrupt change in elevation, allowing stentsegments 32 to slide smoothly from the expandable member 24 to thematerial layer 84. Alternatively, expandable member 24 and/or materiallayer 84 may have an outer diameter or wall thickness that is steppedoutwardly or that gradually increases in the distal direction so as toincrease the frictional resistance with stent segments 32. Inalternative embodiments, material layer 84 may have surface featuressuch as bumps, ridges, projections, or scales to increase frictionagainst stent segments 32.

Annular radiopaque markers 82 may be mounted to the guidewire tube 34,facilitating visualization of the location of balloon member 70 withfluoroscopy and enabling appropriate positioning of stent segments 32 onballoon member 70. Referring to FIG. 2C, the radiopaque markers 82 arepreferably located at regular intervals along the length of theguidewire tube 34. In a particularly preferred form, the radiopaquemarkers 82 are spaced at intervals that are related to the length ofindividual stent segments 32, such as being at intervals equal to thestent segment lengths, one-half of stent segment length, double stentsegment length, or the like. Stated otherwise, the distance between thedistal ends of adjacent markers 82 (or the proximal ends of adjacentmarkers 82, or the mid-points of adjacent markers 82, etc.) are providedequal to the stent segment lengths, one-half of stent segments length,double stent segment length, or the like. Locating multiple radiopaquemarkers 82 on the guidewire tube 34 at regularly spaced intervalsprovides a visual reference for determining the location and number ofstent segments 32 on expandable member 24 under fluoroscopy. Further,the length of expandable member 24 and stent segments 32 exposed duringretraction of sheath 25 may be determined under fluoroscopy by observingthe position of marker 56 on garage member 55 relative to marker(s) 82on guidewire tube 34. Alternatively, only a single marker 82 at or nearthe distal end of balloon member 70 may be used, or markers may beplaced at both the distal end and proximal end of the base member 80, ormarkers may be placed at other locations on nosecone 28, guidewire tube34, or inner shaft 27. Such markers may be made of various radiopaquematerials such as platinum/iridium, tantalum, gold, and other materials.

Stent segments 32 are slidably positioned over balloon member 70.Depending upon the number of stent segments 32 loaded in stent deliverycatheter 20, stent segments 32 may be positioned over both balloonmember 70 and tubular leg 72. In an exemplary embodiment, each stentsegment is about 2-20 mm in length, more preferably 2-8 mm in length,and 3-50 stent segments may be positioned end-to-end in a line overballoon member 70 and tubular leg 72. Stent segments 32 preferably arein direct contact with each other, but alternatively separate spacingelements may be disposed between adjacent stent segments, the spacingelements being movable with the stent segments along balloon member 70.Such spacing elements may be plastically deformable or self-expanding soas to be deployable with stent segments 32 into the vessel, butalternatively could be configured to remain on balloon member 70following stent deployment; for example, such spacing elements couldcomprise elastic rings which elastically expand with balloon member 70and resiliently return to their unexpanded shape when balloon member 70is deflated. The spacing elements could be pushed to the distal end ofballoon member 70 against stop 78 as additional stent segments 32 areadvanced distally.

Stent segments 32 are preferably a malleable metal so as to beplastically deformable by expandable member 24 as they are expanded tothe desired diameter in the vessel. Alternatively, stent segments 32 maybe formed of an elastic or super elastic shape memory material such asNitinol so as to self-expand upon release into the vessel by retractionof sheath 25. Stent segments 32 may also be composed of polymers orother suitable biocompatible materials including bioabsorbable orbioerodable materials. In self-expanding embodiments, expandable member24 may be eliminated or may be used for predilatation of a lesion priorto stent deployment or for augmenting the expansion of theself-expanding stent segments.

In preferred embodiments, stent segments 32 are coated with a drug thatinhibits restenosis, such as Rapamycin, Paclitaxel, Biolimus A9(available from BioSensors International), analogs, prodrugs, orderivatives of the foregoing, or other suitable agent, preferablycarried in a durable or bioerodable polymeric or other suitable carriermaterial. Alternatively, stent segments 32 may be coated with othertypes of drugs and therapeutic materials such as antibiotics,thrombolytics, anti-thrombotics, anti-inflammatories, cytotoxic agents,antiproliferative agents, vasodilators, gene therapy agents, radioactiveagents, immunosuppressants, and chemotherapeutics. Several preferredtherapeutic materials are described in U.S. Published patent applicationNo. 2005/0038505, entitled “Drug-Delivery Endovascular Stent and Methodof Forming the Same,” filed Sep. 20, 2004, which application is herebyincorporated by reference herein. Such materials may be coated over allor a portion of the surface of stent segments 32, or stent segments 32may include apertures, holes, channels, pores, or other features inwhich such materials may be deposited. Methods for coating stentsegments 32 are described in the foregoing published patent application.Various other coating methods known in the art may also be used,including syringe application, spraying, dipping, inkjet printing-typetechnology, and the like.

Stent segments 32 may have a variety of configurations, including thosedescribed in copending application Ser. No. 10/738,666, filed Dec. 16,2003 (Attorney Docket No. 21629-000510), which is incorporated herein byreference. Other preferred stent configurations are described below.Stent segments 32 are preferably completely separate from one anotherwithout any interconnections, but alternatively may have couplingsbetween two or more adjacent segments which permit flexion between thesegments. As a further alternative, one or more adjacent stent segmentsmay be connected by separable or frangible couplings that are separatedprior to or upon deployment, as described in co-pending application Ser.No. 10/306,813, filed Nov. 27, 2002 (Attorney Docket No. 21629-000320),which is incorporated herein by reference.

A pusher tube 86 is slidably disposed over inner shaft 27. The structureof the pusher tube 86 is illustrated in FIG. 13, and its location withinthe catheter body 22 is best shown in FIGS. 2A-B. The pusher tube 86contains three primary sections, a distal extension 88, a ribbon portion89, and a proximal portion 90. The proximal portion 90 extends from thehandle 38 over the inner shaft 27 and to the ribbon portion 89. Theproximal portion 90 is preferably formed of a tubular material toprovide high column strength but adequate flexibility to extend throughthe vasculature from an access site to the coronary ostia or othertarget vascular region. A preferred material is stainless steelhypotube. The ribbon portion 89 of the pusher tube corresponds with thelocation of the guidewire exit port 35 on the outer sheath 25. Theribbon portion 89 is formed of a partial-tube, see, e.g., FIG. 13A, inorder to provide an opening to allow the guidewire tube 34 to passthrough to the exit port 35. The proximal portion of the ribbon portion89 is formed out of the same tubular material that makes up the proximalportion 90 of the pusher tube, e.g., stainless steel hypotube. Theproximal portion of the ribbon portion 89 is joined to the distalportion of the ribbon 89, such as by a weld 91 or the ribbon portion andproximal portion may be formed from the same hypotube which is laser cutin the appropriate geometry. The distal extension 88 is preferablyformed of a slotted tube of rigid material, such as stainless steel orNitinol. The slotted tube making up the distal extension 88 includes anumber of cylindrical rings 92 interconnected by longitudinal connectors93, thereby defining a plurality of transverse slots 97 arranged inpairs along the length of the distal extension. Each pair of slots isdisposed opposite one another on distal extension 88, thus defining apair of opposing, longitudinal connectors 93. The longitudinalconnectors 93 are flexible so as to be capable of bending around atransverse axis. Each pair of transverse slots 97 is oriented at 90degrees relative to the adjacent pair of slots 97, so that the pairs oflongitudinal connectors 93 alternate between those oriented verticallyand those oriented horizontally. This allows distal extension 88 to bendabout either a horizontal and vertical transverse axes, thus providing ahigh degree of flexibility. Of course, the pairs of transverse slots 97could be oriented at various angles relative to adjacent pairs toprovide flexibility about more than two axes. The slots provided in theslotted tube allows the distal extension 88 to be more axially flexiblethan it would be without the slots, while still retaining high columnstrength. It is preferable to provide transverse slots 97 andcylindrical rings 92 that each have a width that is approximately thesame as the length of a stent segment 32. In addition or alternatively,the transverse slots 97 and cylindrical rings 92 may be spaced apart bya known fraction or multiple of the stent segment length. In this way, adetent mechanism may be provided on the interior surface of the sheath25, with one or more detents that releasably engage the cylindricalrings 92 formed in the distal extension 88 to provide a tactile feedbackbased upon the distance that the outer sheath 25 is retracted relativeto pusher tube 86. A nesting tip 94 is formed on the distal end of thedistal extension 88. The nesting tip preferably includes a plurality offingers shaped and oriented to engage and interleave with the proximalend of the most proximal stent segment 32. As described elsewhereherein, stent segments 32 preferably have axial extensions orprojections on each end which interleave with those on the adjacentstent segment. Tip 94 of pusher tube 86 preferably has a geometry withaxial projections similar to or complementary to those of stent segments32 so as to interleave therewith.

Preferably, the proximal portion 90 of the pusher tube has a diameterthat is smaller than the diameter of the distal extension 88. Thus, thestainless steel hypotube material making up the proximal portion 90 ofthe pusher tube and part of the ribbon portion 89 may have a firstdiameter, while the slotted tube making up the distal extension 88 andthe distal portion of the ribbon 89 may have a second, larger diameter.As noted above, the slotted tube and the hypotube are preferably joinedby a weld 91 formed in the ribbon portion 89.

As best shown in FIGS. 2A-B, the pusher tube 86 extends longitudinallywithin the outer sheath 25 and over the inner shaft 27 through most ofthe length of the catheter body 22. The distal extension 88 is slidableover the tubular leg 72 and engages the stent segment 32 at the proximalend of the line of stent segments 32. At its proximal end (not shown),the pusher tube 86 is coupled to an actuator associated with the handle38 (see FIG. 1). In this way, the pusher tube 86 can be advanceddistally relative to inner shaft 27 to urge the stent segments 32distally over the expandable member 24 (or, alternatively, the pushertube 86 may be held in position while retracting the expandable member24 relative to stent segments 32) until the stent segments engage thestop 78. In addition, the pusher tube 86 can be used to hold the stentsegments 32 in place on the expandable member 24 while the sheath 25 isretracted to expose a desired number of stent segments 32, as shown inFIG. 2B. As noted above, the proximal portion 90, ribbon portion 89, anddistal extension 88 of the pusher tube are preferably constructed ofstainless steel, but they may alternatively be constructed of a varietyof biocompatible polymers, metals, polymer/metal composites, alloys, orthe like.

It can be seen that with sheath 25 retracted a desired distance,expandable member 24 is allowed to expand when inflation fluid isdelivered through inflation lumen 66, thereby expanding a desired numberof stent segments 32 exposed distally of sheath 25. The remainingportion of expandable member 24 and the remaining stent segments 32within sheath 25 are constrained from expansion by sheath 25.

FIG. 2B further illustrates that when sheath 25 is retracted relative toexpandable member 24, guidewire tube exit port 35 becomes further awayfrom the point at which guidewire 36 exits the proximal end 74 oftubular leg 72, increasing the distance that guidewire 36 must passwithin the interior of sheath 25. Advantageously, guidewire tube 34provides a smooth and continuous passage from the tubular leg 72 throughguidewire tube exit port 35, eliminating any problems that might resultfrom changing the alignment of the two. This is particularly importantin the present invention where the stent delivery catheter may carry alarge number of stent segments 32 and sheath 25 may be retracted asubstantial distance relative to expandable member 24, resulting insubstantial misalignment of guidewire tube exit port 35 relative totubular leg 72.

In order to confirm the positioning of the stent segments 32 on theexpandable member 24, fluoroscopy is used to visualize the stentsegments 32 relative to the markers 82 located on the inner shaft 27. Inaddition, by fluoroscopic visualization of the marker 56 located on thegarage 55 at the distal end of the outer sheath 25, the user can see theextent of retraction of the sheath 25 relative to the expandable member24 and view the location of the exposed stent segments 32 relative tothe sheath 25. Visualization of the stent segments 32 is furtherenhanced with the use of radiopaque markers and/or materials in or onthe stent segments themselves. Markers of radiopaque materials may beapplied to the exterior of stent segments 32, e.g, by applying a metalsuch as gold, platinum, a radiopaque polymer, or other suitable coatingor mark on all or a portion of the stent segments. Examples of suchmarkers are illustrated in FIGS. 14A-B. In those Figures, radiopaquemarkers 95 are attached to a plurality of circular openings formed inthe body of the stent segment 32. Six such markers are formed in acircumferentially aligned pattern in the FIG. 14A example, while threemarkers are formed in another circumferentially aligned pattern in theFIG. 14B example. The markers may be discs, buttons, or other membersthat are welded in place, or they may be provided as rivets orrivet-type members that are installed in a sized hole or eyelet.Alternatively, stent segments 32 may include a radiopaque cladding orcoating or may be composed of radiopaque materials such as L-605 cobaltchromium (ASTM F90), other suitable alloys containing radiopaqueelements, or multilayered materials having radiopaque layers. See, forexample, FIGS. 15A-C, where three patterns of radiopaque coatings areillustrated. In FIG. 15A, a coating 96 of radiopaque material isprovided in a broad circumferential center stripe on the stent segment32. In FIGS. 15B and C, smaller circumferential stripes of radiopaquecoatings 96 are formed on the proximal and distal ends of the stentsegment 32, such as being formed only on the axial projection portionsof the stent segment 32 (see FIG. 15C). In yet another alternative,stent segments 32 may have a geometry conducive to fluoroscopicvisualization, such as having struts of greater thickness, sections ofhigher density, or overlapping struts.

Preferably, the radiopaque markers are configured so as to provide anindication of the number, location, and/or relative spacing of eachstent segment 32 when deployed end-to-end in a line in a vessel or otherbody lumen. This allows the operator to determine how many stentsegments 32 have been deployed at a vascular site, and the spacingbetween adjacent stent segments 32. The radiopaque markers allow theoperator to visualize with fluoroscopy the divisions between adjacentstent segments 32 by observing radiopaque markers on the ends and/or amiddle portions of each stent segment 32. For example, in the embodimentof FIG. 15D, the operator may visualize a central stripe on each segmentto allow an accounting of the number and location of deployed segments32. In the embodiments of FIG. 15E, the operator may visualize twoadjacent radiopaque stripes where two segment ends are disposedside-by-side. If the segments are close together, the operator sees asingle wide stripe, while if the segments are separated by a gap, theoperator may see two parallel stripes, thus providing an indication ofthe segment spacing as well as number.

Some of the possible materials that may be used in stent segments 32include (by ASTM number):

F67-00 Unalloyed Titanium

F75-01 Cobalt-28 Chromium-6 Molybdenum Alloy

F90-01 Wrought Cobalt-20 Chromium-15 Tungsten-10 Nickel Alloy

F136-02a Wrought Titanium-6 Aluminum-4 Vanadium ELI Alloy

F138-00, F139-00 Wrought 18 Chromium-14 Nickel-2.5 Molybdenum StainlessSteel Bar or Sheet

F560-98 Unalloyed Tantalum

F562-02 Wrought 35 Cobalt-35 Nickel-20 Chromium-10 Molybdenum Alloy

F563-00 Wrought Cobalt-20 Nickel-20 Chromium 3.5 Molybdenum-3.5Tungste-5 Iron Alloy

F688 Wrought Cobalt-35 Nickel-20 Chromium-10 Molybdenum Alloy

F745-00 18 Chromium-12.5 Nickel-2.5 Molybdenum Stainless Steel

F799-02 Cobalt-28 Chromium-6 Molybdenum Alloy

F961-96 Cobalt-35 Nickel-20 Chromium-10 Molybdenum Alloy

F1058-02 Wrought 40 Cobalt-20 Chromium-16 Iron-15 Nickel-7 MolybdenumAlloy

F1091-02 Wrought Cobalt-20 Chromium-15 Tungsten-10 Nickel Alloy

F1108 Titanium-6 Aluminum-4 Vanadium Alloy

F1295-01 Wrought Titanium-6 Aluminum-7 Niobium Alloy

F1314-01 Wrought Nitrogen-strengthened 22 Chromium-13 Nickel-5Manganese-2.5 Molybdenum Stainless Steel Alloy

F1241-99 Unalloyed Titanium Wire

F1350-02 Wrought 18 Chromium-14 Nickel-2.5 Molybdenum Stainless SteelWire

F1377-98a Cobalt-28 Chromium-6 Molybdenum Powder coating

F1472-02a Wrought Titanium-6 Aluminum-4 Vanadium Alloy

F1537-00 Wrought Cobalt-28 Chromium-6 Molybdenum Alloy

F1580-01 Titanium and Titanium-6 Aluminum-4 Vanadium Alloy Powdercoating

F1586-02 Wrought Nitrogen Strengthened 21 Chromium-10 Nickel-3Mnaganese-2.5 Molybdenum Stainless Steel Bar

F1713-96 Wrought Titanium-13 Niobium-13 Zirconium Alloy

F1813-01 Wrought Titanium-12 Molybdenum-6 Zirconium-2 Iron Alloy

F2063-00 Wrought Nickel-Titanium Shape Memory Alloys

F2066-01 Wrought Titanium-15 Molybdenum Alloy

F2146-01 Wrought Titanium-3 Aluminum-2.5 Vanadium Alloy Seamless Tubing

F2181-02a Wrought Stainless Steel Tubing.

FIGS. 5A-B illustrate a portion of a first embodiment of a stent segment32.

-   The Figures illustrate a portion of the stent segment 32 in a planar    shape for clarity. The stent segment 32 includes two parallel rows    98A, 98B of I-shaped cells 100 formed into a cylindrical shape    around an axial axis A. Each cell 100 includes upper and lower axial    slots 102 and a connecting circumferential slot 104. The upper and    lower slots 102 are bounded by upper axial struts 106, lower axial    struts 107, curved outer ends 108 and curved inner ends 110. Each    circumferential slot 104 is bounded by an outer circumferential    strut 109 and an inner circumferential strut 111. Each I-shaped cell    100 is connected to the adjacent I-shaped cell 100 in the same row    98A or 98B by a circumferential connecting strut 113. All or a    portion of cells 100 in row 98A merge or join with cells 100 in row    98B at the inner ends 110, which are integrally formed with the    inner ends 110 of the adjacent cells 100.

In a preferred embodiment, a spacing member 112 extends outwardly in theaxial direction from a selected number of outer circumferential struts109 and/or connecting struts 113. Spacing member 112 preferably itselfforms a subcell 114 in its interior, but alternatively may be solidwithout any cell or opening therein. For those spacing members 112attached to outer circumferential struts 109, subcell 114 preferablycommunicates with I-shaped cell 100. Spacing members 112 are configuredto engage the curved outer ends 108 of an adjacent stent segment 32 soas to maintain appropriate spacing between adjacent stent segments. Inone embodiment, spacing members 112 have outer ends 116 with twospaced-apart protrusions 118 that provide a cradle-like structure toindex and stabilize the curved outer end 108 of the adjacent stentsegment. Preferably, spacing members 112 have an axial length of atleast about 10%, more preferably at least about 25%, of the longdimension L of I-shaped cells 100, so that the I-shaped cells 100 ofadjacent stent segments are spaced apart at least that distance. Becausespacing members 112 experience little or no axial shortening duringexpansion of stent segments 32, this minimum spacing between stentsegments is maintained both in the unexpanded and expandedconfigurations.

FIG. 5B shows stent segment 32 of FIG. 5A in an expanded configuration.It may be seen that cells 100 are expanded so that upper and lower slots102 are diamond shaped with circumferential slots 104 remainingbasically unchanged. This results in some axial shortening of the stentsegment, thereby increasing the spacing between adjacent stent segments.The stent geometry is optimized by balancing the amount of axialshortening and associated inter-segment spacing, the desired degree ofvessel wall coverage, the desired metal density, and other factors.Because the stent is comprised of multiple unconnected stent segments32, any desired number from 2 up to 10 or more stent segments may bedeployed simultaneously to treat lesions of any length. Further, becausesuch segments are unconnected to each other, the deployed stentstructure is highly flexible and capable of deployment in long lesionshaving curves and other complex shapes.

As an additional feature, circumferential slots 104 provide a pathwaythrough which vessel side branches can be accessed for catheterinterventions. Should stent segment 32 be deployed at a location inwhich it covers the ostium of a side branch to which access is desired,a balloon dilatation catheter may be positioned through circumferentialslot 104 and expanded. This deforms circumferential struts 109, 111axially outward, thereby expanding circumferential slot 104 and furtherexpanding upper and lower slots 102, as shown in phantom in FIG. 5B.This provides a relatively large opening 120 through which a cathetermay be inserted through stent segment 32 and into the side branch forplacing stents, performing angioplasty, or carrying out otherinterventions.

FIGS. 6A-6B illustrate a second embodiment of a stent segment 32according to the invention. In FIG. 6A, a portion of stent segment 32 isshown in a planar shape for clarity. Similar to the embodiment of FIG.5A, stent segment 32 comprises two parallel rows 122A, 122B of I-shapedcells 124 formed into a cylindrical shape around axial axis A. Cells 124have upper and lower axial slots 126 and a connecting circumferentialslot 128. Upper and lower slots 126 are bounded by upper axial struts130, lower axial struts 132, curved outer ends 134, and curved innerends 136. Circumferential slots 128 are bounded by outer circumferentialstrut 138 and inner circumferential strut 140. Each I-shaped cell 124 isconnected to the adjacent I-shaped cell 124 in the same row 122 by acircumferential connecting strut 142. Row 122A is connected to row 122Bby the merger or joining of curved inner ends 136 of at least one (andpreferably three) of upper and lower slots 126 in each cell 124.

One of the differences between the embodiment of FIGS. 6A-6B and that ofFIGS. 5A-5B is the way in which spacing is maintained between adjacentstent segments. In place of the spacing members 112 of the earlierembodiment, the embodiment of FIG. 6A includes a bulge 144 in upper andlower axial struts 130, 132 extending circumferentially outwardly fromaxial slots 126. These give axial slots 126 an arrowhead or cross shapeat their inner and outer ends. The bulge 144 in each upper axial strut130 extends toward the bulge 144 in a lower axial strut 132 in the samecell 100 or in an adjacent cell 100, thus creating a concave abutment146 in the space between each axial slot 126. Concave abutments 146 areconfigured to receive and engage curved outer ends 134 of cells 124 inthe adjacent stent segment, thereby maintaining spacing between thestent segments. The axial location of bulges 144 along upper and loweraxial struts 130, 132 may be selected to provide the desired degree ofinter-segment spacing.

FIG. 6B shows two stent segments 32 of FIG. 6A in an expanded condition.It may be seen that axial slots 124 are deformed into acircumferentially widened modified diamond shape with bulges 144 on thenow diagonal upper and lower axial struts 130, 132. Circumferentialslots 128 are generally the same size and shape as in the unexpandedconfiguration. Bulges 144 have been pulled away from each other to someextent, but still provide a concave abutment 146 to maintain a minimumdegree of spacing between adjacent stent segments. As in the earlierembodiment, some axial shortening of each segment occurs upon expansionand stent geometry can be optimized to provide the ideal intersegmentspacing.

It should also be noted that the embodiment of FIGS. 6A-6B retains thefeature described above with respect to FIGS. 5A-5B to enable access tovessel side branches blocked by stent segment 32. Should such sidebranch access be desired, a dilatation catheter may be inserted intocircumferential slot 128 and expanded to provide an enlarged openingthrough which a side branch may be entered.

Referring now to FIGS. 7A-7E, the use of the stent delivery catheter ofthe invention will be described. While the invention will be describedin the context of coronary artery treatment, it should be understoodthat the invention is useful in any of a variety of blood vessels andother body lumens in which stents are deployed, including the carotid,femoral, iliac and other arteries, as well as veins and otherfluid-carrying vessels. A guiding catheter (not shown) is first insertedinto a peripheral artery such as the femoral and advanced to the ostiumof the target coronary artery. A guidewire GW is then inserted throughthe guiding catheter into the coronary artery A where lesion L is to betreated. The proximal end of guidewire GW is then inserted throughnosecone 28 and guidewire tube 34 outside the patient's body and stentdelivery catheter 20 is slidably advanced over guidewire GW and throughthe guiding catheter into the coronary artery A. Slider assembly 50 ispositioned within the hemostasis valve at the proximal end of theguiding catheter, which is then tightened to provide a hemostatic sealwith the exterior of the slider body 52. Stent delivery catheter 20 ispositioned through a lesion L to be treated such that nosecone 28 isdistal to lesion L. During this positioning, sheath 25 is positioneddistally up to nosecone 28 so as to surround expandable member 24 andall of the stent segments 32 thereon.

Optionally, lesion L may be pre-dilated prior to stent deployment.Pre-dilation may be performed prior to introduction of stent deliverycatheter 20 by inserting an angioplasty catheter over guidewire GW anddilating lesion L. Alternatively, stent delivery catheter 20 may be usedfor pre-dilation by retracting sheath 25 along with stent segments 32 toexpose an extremity of expandable member 24 long enough to extendthrough the entire lesion. This may be done while delivery catheter 20is positioned proximally of lesion L or with expandable member 24extending through lesion L. Fluoroscopy enables the user to visualizethe extent of sheath retraction relative to lesion L by observing theposition of marker 56 on the garage 55 contained at the distal end ofthe sheath 25 relative to the markers 82 formed on the guidewire tube 34beneath the expandable member 24. To allow stent segments 32 to moveproximally relative to expandable member 24, force is released frompusher tube 86 and valve member 58 engages and draws the stent segmentsproximally with sheath 25. The pusher tube 86 is retracted along withthe outer sheath 25 by use of an actuator provided on the handle 38.With the appropriate length of expandable member 24 exposed, expandablemember 24 is positioned within lesion L and inflation fluid isintroduced through inflation lumen 66 to inflate expandable member 24distally of sheath 25 and thereby dilate lesion L. Expandable member 24is then deflated and retracted within sheath 25 while maintaining forceon pusher tube 86 so that stent segments 32 are positioned up to thedistal end of expandable member 24, surrounded by sheath 25.

Following any predilatation, stent delivery catheter 20 is repositionedin artery A so that nosecone 28 is distal to lesion L as shown in FIG.7A. Sheath 25 is then retracted as in FIG. 7B to expose the appropriatenumber of stent segments 32 to cover lesion L. Again, fluoroscopy can beused to visualize the position of sheath 25 by observing marker 56thereon relative to marker 82 within expandable member 24. As sheath 25is drawn proximally, force is maintained against pusher tube 86 so thatstent segments 32 remain positioned up to the distal end of expandablemember 24. It should also be noted that sheath 25 moves proximallyrelative to guidewire tube 34, which slides through guidewire tube exitport 35. Advantageously, regardless of the position of sheath 25,guidewire tube 34 provides a smooth and continuous passage for guidewireGW so that stent delivery catheter slides easily over guidewire GW.

With the desired number of stent segments 32 exposed distally of sheath25, it is preferable to create some spacing between the stent segmentsto be deployed and those remaining enclosed within the sheath 25. Thisreduces the risk of dislodging or partially expanding the distal-moststent segment 32 within sheath 25 when expandable member 24 is inflated.Such spacing is created, as shown in FIG. 7C, by releasing force againstpusher tube 86 and retracting both the pusher tube 86 and the sheath 25a short distance simultaneously. The engagement of valve member 58 withstent segments 32 moves those stent segments 32 within sheath 25 awayfrom those stent segments 32 distal to sheath 25. The length of thisspacing is preferably equal to the length of about ½-1 stent segment,e.g., in one embodiment about 2-4 mm. By observing radiopaque marker 56on sheath 25, the operator can adjust the spacing to be suitable incomparison to the length of marker 56, which preferably has a lengthequal to the desired spacing distance.

Expandable member 24 is then inflated by delivering inflation fluidthrough inflation lumen 66, as shown in FIG. 7D. The exposed distalportion of expandable member 24 expands so as to expand stent segments32 thereon into engagement with lesion L. If predilatation was notperformed, lesion L may be dilated during the deployment of stentsegments 32 by appropriate expansion of expandable member 24. Sheath 25constrains the expansion of the proximal portion of expandable member 24and those stent segments 32 within sheath 25.

Expandable member 24 is then deflated, leaving stent segments 32 in aplastically-deformed, expanded configuration within lesion L, as shownin FIG. 7E. The alternative embodiment of stent segment 32 illustratedin FIGS. 6A-6B is shown in a similarly expanded condition in FIG. 8.With stent segments 32 deployed, expandable member 24 may be retractedwithin sheath 25, again maintaining force against pusher tube 86 toslide stent segments 32 toward the distal end of expandable member 24.Expandable member 24 is moved proximally relative to stent segments 32until the distal-most stent segment engages stop 78 (FIGS. 2A-2B),thereby placing stent segments 32 in position for deployment. Stentdelivery catheter 20 is then ready to be repositioned at a differentlesion in the same or different artery, and additional stent segmentsmay be deployed. During such repositioning, guidewire tube 34facilitates smooth tracking over guidewire GW. Advantageously, multiplelesions of various lengths may be treated in this way without removingstent delivery catheter 20 from the patient's body. Should there be aneed to exchange stent delivery catheter 20 with other catheters to beintroduced over guidewire GW, guidewire tube 34 facilitates quick andeasy exchanges.

It should be understood that when the movement of the pusher tube,sheath, or stent segments is described in relation to other componentsof the delivery catheter of the invention, such movement is relative andwill encompass both moving the sheath, pusher tube, or stent segmentswhile keeping the other component(s) stationary, keeping the sheath,pusher tube or stent segments stationary while moving the othercomponent(s), or moving multiple components simultaneously relative toeach other.

While the foregoing description of the invention is directed to a stentdelivery catheter for deploying stents into vascular lumens to maintainpatency, it should be understood that various other types of wire-guidedcatheters also may embody the principles of the invention. For example,balloon catheters for angioplasty and other purposes, particularly thosehaving a slidable external sheath surrounding the balloon, may beconstructed in accordance with the invention. Other types of cathetersfor deployment of prosthetic devices such as embolic coils, stentgrafts, aneurism repair devices, annuloplasty rings, heart valves,anastomosis devices, staples or clips, as well as ultrasound andangiography catheters, electrophysiological mapping and ablationcatheters, and other devices may also utilize the principles of theinvention.

Although the above is complete description of the preferred embodimentsof the invention, various alternatives, additions, modifications andimprovements may be made without departing from the scope thereof, whichis defined by the claims.

1. Apparatus for delivering a prosthesis into a target vessel of apatient, comprising: a flexible catheter shaft having proximal anddistal ends; an expandable member attached to the catheter shaft nearthe distal end thereof; a tubular prosthesis releasably carried near thedistal end of the catheter shaft and being positionable over theexpandable member for expansion therewith; and a stop member coupled toone or both of the catheter shaft and the expandable member, said stopmember being configured to substantially inhibit distal movement of saidtubular prosthesis beyond a predetermined position.
 2. The apparatus ofclaim 1, wherein said stop member comprises a partial cylindrical memberattached to the catheter shaft having a pair of opposed relief regions.3. The apparatus of claim 2 wherein the relief regions are flat areas onthe partial cylindrical member.
 4. The apparatus of claim 1, whereinsaid stop member comprises a layer of a first material located on anexternal surface of the expandable member, the first material having ahigher coefficient of friction than the expandable member.
 5. Theapparatus of claim 4, wherein said first material comprises a polymericmaterial.
 6. The apparatus of claim 4, wherein said first materialcomprises a polyurethane.
 7. The apparatus of claim 4, wherein saidlayer of material is a continuous layer located on said expandablemember.
 8. The apparatus of claim 4, wherein said layer of material isdiscontinuous on said expandable member.
 9. The apparatus of claim 4,wherein said layer of material is located in an embedded region of theexpandable member such that the layer of material and the expandablemember have a substantially continuous surface.
 10. The apparatus ofclaim 4, wherein said layer of material has a thickness that increasesin the distal direction.
 11. The apparatus of claim 4, wherein saidlayer of material is provided with one or more surface features selectedfrom the group consisting of bumps, ridges, projections, or scales. 12.A method for delivering a prosthesis in a target vessel of a patient,comprising: inserting a guidewire through the patient's vasculature tothe target vessel; slidably coupling a catheter to the guidewire, thecatheter having an outer sheath and an inner shaft, and having anexpandable member attached to a distal end thereof; advancing thecatheter over the guidewire to the target vessel; retracting the outersheath relative to the inner shaft to expose a first tubular prosthesiscarried on the expandable member; expanding the expandable member todeploy the first tubular prosthesis in the target vessel; and causingrelative longitudinal motion between the expandable member and a secondprosthesis in the catheter until the second prosthesis engages a stopmember attached to a distal portion of the catheter.
 13. The method ofclaim 12, wherein said stop member comprises a partial cylindricalmember having a pair of opposed relief regions.
 14. The method of claim12, wherein said stop member comprises a layer of a first materiallocated on an external surface of the expandable member.
 15. The methodof claim 14, wherein said first material comprises a polymeric material.16. The method of claim 14, wherein said first material comprises apolyurethane.
 17. The method of claim 14, wherein said layer of materialis a continuous layer located on said expandable member.
 18. The methodof claim 14, wherein said layer of material is discontinuous on saidexpandable member.
 19. The method of claim 14, wherein said layer ofmaterial is located in an embedded region of the expandable member suchthat the layer of material and the expandable member have asubstantially continuous surface.
 20. The method of claim 14, whereinsaid layer of material has a thickness that increases in the distaldirection.
 21. The method of claim 14, wherein said layer of material isprovided with one or more surface features selected from the groupconsisting of bumps, ridges, projections, or scales.
 22. The method ofclaim 12, further comprising covering a proximal portion of theexpandable member by the outer sheath to constrain the proximal portionfrom expansion while a distal portion of the expandable member expands.23. The method of claim 12, wherein the first tubular prosthesiscomprises a plurality of prosthesis segments, further comprisingpositioning a first selected number of the prosthesis segments on theexpandable member for expansion therewith.
 24. Apparatus for deliveringa prosthesis into a target vessel of a patient, comprising: a flexiblecatheter having proximal and distal ends, said catheter comprising anouter sheath, a pusher shaft, and an inner shaft; a plurality of tubularprostheses releasably carried near the distal end of the catheter overthe inner shaft, the outer sheath disposed over the prostheses and beingaxially movable relative thereto, a distal end of the pusher shaftabutting a proximal end of one of the tubular prostheses; and aplurality of radiopaque markers located near the distal end of saidcatheter, each of said plurality of radiopaque markers being spaced at aregular interval in relation to each adjacent radiopaque marker.
 25. Theapparatus of claim 24, wherein each of said plurality of prostheses hasa first length, and further wherein the radiopaque markers are separatedby a distance equal to a predetermined fraction or multiple of the firstlength.
 26. The apparatus of claim 25 wherein the radiopaque markers areseparated by a distance equal to the first length.
 27. The apparatus ofclaim 25 wherein each radiopaque marker has an axial width that is apredetermined fraction or multiple of the first length.
 28. Theapparatus of claim 25 wherein the radiopaque markers are separated by adistance and have an axial width, wherein the sum of the distance andthe axial width is equal to the first length.
 29. The apparatus of claim24, wherein said plurality of radiopaque markers are attached to saidinner shaft of said catheter.